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J Thorac Cardiovasc Surg 2006;132:839-844
© 2006 The American Association for Thoracic Surgery

Surgery for Congenital Heart Disease

Brain oxygen and metabolism during circulatory arrest with intermittent brief periods of low-flow cardiopulmonary bypass in newborn piglets

^a Department of Pediatrics, University of Miami, Miami, Fla
^b Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia, Pa
^c Department of Anesthesiology and Critical Care Medicine, Mayo Clinic, Rochester, Minn
^d Department of Anesthesiology and Critical Care Medicine, Children's Hospital of Philadelphia, Philadelphia, Pa
^e Department of Surgery, University of Oklahoma, Oklahoma City, Okla

^_* Address for reprints: Anna Pastuszko, PhD, Department Biochemistry and Biophysics, School of Medicine, 264 Anatomy Chemistry Bldg, University of Pennsylvania, Philadelphia, PA 19104. (Email: pastuszk{at}mail.med.upenn.edu).

Objective: We performed this study to determine whether brief intermittent periods of low-flow cardiopulmonary bypass during deep hypothermic circulatory arrest would improve cortical metabolic status and prolong the "safe" time of deep hypothermic circulatory arrest.

Methods: After a 2-hour baseline, newborn piglets were placed on cardiopulmonary bypass and cooled to 18°C. The animals were then subjected to 80 minutes of deep hypothermic circulatory arrest interrupted by 5-minute periods of low-flow cardiopulmonary bypass at either 20 mL · kg^–1 · min^–1 (LF-20) or 80 mL · kg^–1 · min^–1 (LF-80) during 20, 40, 60, and 80 minutes of deep hypothermic circulatory arrest. All animals were rewarmed, separated from cardiopulmonary bypass, and maintained for 2 hours (recovery). The oxygen pressure in the cerebral cortex was measured by the quenching of phosphorescence. The extracellular dopamine level in the striatum was determined by microdialysis. Results are means ± SD.

Results: Prebypass oxygen pressure in the cerebral cortex was 65 ± 7 mm Hg. During the first 20 minutes of deep hypothermic circulatory arrest, cortical oxygen pressure decreased to 1.3 ± 0.4 mm Hg. Four successive intermittent periods of LF-20 increased cortical oxygen pressure to 6.9 ± 1.2 mm Hg, 6.6 ± 1.9 mm Hg, 5.3 ± 1.6 mm Hg, and 3.1 ± 1.2 mm Hg. During the intermittent periods of LF-80, cortical oxygen pressure increased to 21.1 ± 5.3 mm Hg, 20.6 ± 3.7 mm Hg, 19.5 ± 3.95 mm Hg, and 20.8 ± 5.5 mm Hg. A significant increase in extracellular dopamine occurred after 45 minutes of deep hypothermic circulatory arrest alone, whereas in the groups of LF-20 and LF-80, the increase in dopamine did not occur until 52.5 and 60 minutes of deep hypothermic circulatory arrest, respectively.

Conclusions: The protective effect of intermittent periods of low-flow cardiopulmonary bypass during deep hypothermic circulatory arrest is dependent on the flow rate. We observed that a flow rate of 80 mL · kg^–1 · min^–1 improved brain oxygenation and prevented an increase in extracellular dopamine release.

This article has been cited by other articles:

				P. Pastuszko, H. Liu, A. Mendoza-Paredes, S. E. Schultz, S. D. Markowitz, W. J. Greeley, D. F. Wilson, and A. Pastuszko Brain oxygen and metabolism is dependent on the rate of low-flow cardiopulmonary bypass following circulatory arrest in newborn piglets Eur. J. Cardiothorac. Surg., May 1, 2007; 31(5): 899 - 905. [Abstract] [Full Text] [PDF]